Small Modular Reactors: Can Nuclear Power Reinvent Itself for the 2030s?

What Makes a Reactor "Small" and "Modular"

Conventional nuclear power plants are large. A typical pressurized water reactor produces 1,000–1,600 MW of electricity and takes 10–20 years and $10–$30 billion to build. Small modular reactors, by definition, produce no more than 300 MW of electrical output — and most designs target 50–175 MW. The "modular" part refers to factory fabrication: instead of building a unique, custom reactor on-site, SMR components are manufactured in a factory to standardized specifications and shipped to the site for assembly.

The premise is compelling. Factory manufacturing should improve quality control, reduce construction time, and allow cost reductions through repetition — the same logic that made commercial aviation economical over time. Smaller size should reduce financial risk, since a developer commits a few billion dollars rather than $30 billion. And SMRs' smaller footprint should make them deployable on sites unsuitable for conventional nuclear plants.

The question is whether that premise translates to reality — and the honest answer is that the jury is still out, with one crucial data point about to arrive.

China's Linglong One: The World's First Commercial SMR

China's ACP100 reactor, branded "Linglong One," is a 125 MWe pressurized water reactor under construction at Changjiang, Hainan Province. It is expected to achieve commercial operation by the end of 2026, making it the first commercial small modular reactor anywhere in the world.

The ACP100 was designed by the China National Nuclear Corporation specifically as an SMR: integral reactor design (steam generators inside the reactor vessel rather than external), passive safety systems, and compact size. It has been under construction since 2021 after receiving regulatory approval in 2021.

The ACP100's performance data — its actual construction time, final cost, and operational reliability once it comes online — will be closely watched by the global nuclear industry. China has the regulatory framework, industrial supply chain, and financing conditions to execute nuclear projects efficiently. Whether the ACP100's economics prove out SMR theory in a favorable environment will say a great deal about what is achievable elsewhere.

Rolls-Royce SMR: The UK Bid

Rolls-Royce SMR, a consortium including BNF Technology and several partners, is developing a 470 MWe reactor design (larger than most SMR definitions, sometimes called an "advanced modular reactor") for deployment in the United Kingdom. The UK government has provided significant financial support through Great British Nuclear and Rolls-Royce has submitted its design for Generic Design Assessment by the UK nuclear regulator.

The company is targeting three or more sites in the UK, with Wylfa in Wales often mentioned as a potential first location. Targeting mid-2030s first operation. The Rolls-Royce design aims to hit £2.5 billion per reactor after the first units demonstrate the production learning curve — a cost target that would make it competitive with offshore wind in the UK.

US SMR Development: After NuScale's Cancellation

The US SMR landscape suffered a significant setback in November 2023 when NuScale Power cancelled its VOYGR project — a 6-module, 462 MWe plant planned for the Idaho National Laboratory site — citing cost overruns. Project costs had escalated from initial estimates of $5.3 billion to revised estimates approaching $9.3 billion, and the Utah Associated Municipal Power Systems utility consortium that had agreed to purchase the power withdrew when costs made the project uncompetitive against alternatives.

The NuScale cancellation was a genuine blow to US SMR credibility. NuScale had spent over a decade developing its design, received the first SMR design approval from the US Nuclear Regulatory Commission in 2020, and was widely considered the most advanced US SMR project. The cost escalation reflected real challenges: NuScale's factory-fabricated modules were larger than easy transportation permitted, requiring field assembly that limited the efficiency gains of factory manufacturing.

US Players Still Active

TerraPower: Founded with backing from Bill Gates, TerraPower is developing the Natrium reactor — a 345 MWe sodium-cooled fast reactor with a molten salt thermal energy storage system that allows it to vary output to complement wind and solar. The Natrium demonstration project is planned for Kemmerer, Wyoming, targeting first power in 2030. The design is technically ambitious but has not yet completed NRC design review.

X-Energy: X-Energy is developing the Xe-100, a 80 MWe pebble bed high-temperature gas reactor. It has a partnership with Dow Chemical to provide process heat for industrial applications — a potentially important use case, since industrial heat decarbonization is challenging. Targeting a demonstration project in the late 2020s with DOE funding under the Advanced Reactor Demonstration Program.

Kairos Power: Developing a fluoride salt-cooled high-temperature reactor. Has received NRC approval to construct a test reactor called Hermes at Oak Ridge, Tennessee — the first non-water-cooled reactor approved for US construction in decades. Hermes will not generate commercial electricity but will validate the technology before commercial deployment.

The Cost Challenge: Why SMRs Haven't Delivered Cheaper Nuclear Yet

Nuclear economics operate on a fundamental tension: nuclear power plants have high upfront capital costs but low fuel and operating costs, giving them a levelized cost that depends heavily on discount rates and construction risk. The history of Western nuclear construction — particularly the Vogtle Units 3 and 4 in Georgia, which came online in 2023–2024 at roughly $35 billion versus an original $14 billion estimate — demonstrates how badly construction cost overruns can destroy the economics of nuclear projects.

SMRs theoretically solve this by making nuclear projects smaller and faster to build. But the cost advantage has not yet materialized in practice:

• Small reactors lose the economies of scale of larger plants — you need more reactors, each with their own control room, safety systems, and regulatory compliance overhead, to produce equivalent output
• Factory manufacturing savings depend on high production volumes — which require a large market, which does not yet exist
• Regulatory costs are substantial regardless of reactor size
• Construction labor costs in Western countries are high and difficult to reduce through modularization

The DOE estimates first-of-kind SMRs will cost $3,000–$5,000 per kW, with costs declining to $2,000–$3,500 per kW for nth-of-a-kind plants. Wind currently costs $1,500–$2,000 per kW; utility solar around $1,000–$1,500 per kW. Nuclear's cost advantage must come from factors other than capital cost — specifically, its 24/7 availability and tiny land footprint.

Why Nuclear Still Matters for Decarbonization

The argument for nuclear is not that it is cheap. It is that the grid needs 24/7 carbon-free power, and there are not many ways to provide it. Hydropower is the main existing source of dispatchable clean electricity, but it is geographically limited and largely already built out. Geothermal baseload is confined to specific geologies. Long-duration storage is improving but not yet scalable enough to firm a winter grid entirely powered by wind and solar.

Nuclear's land footprint is also dramatically smaller than renewable energy. A 1,000 MW nuclear plant occupies roughly 1–2 square miles. Producing equivalent average output from wind would require approximately 250–300 square miles of wind farm (accounting for capacity factor). In densely populated regions or areas with land constraints, this matters.

SMRs add two capabilities conventional nuclear lacks: the ability to follow load (some designs can ramp output more quickly than large plants) and deployment in smaller increments. A utility can add 100 MW of SMR capacity, then add another 100 MW a few years later as demand grows, rather than committing to a 1,600 MW project all at once.

Realistic Timeline

For SMRs to be commercially significant in US electricity generation, the realistic timeline is the mid-to-late 2030s — assuming regulatory approvals proceed, Linglong One and other first movers demonstrate favorable economics, and construction supply chains develop. This is not a technology that will materially affect electricity supply in the next 5 years. For the 2030 grid, wind, solar, and storage are the dominant story. For the 2040 grid, SMRs may play a meaningful role in providing firm clean power to complement variable renewables.

For context on other non-solar energy technologies, see our coverage of tidal and wave energy and the broader picture in onshore vs offshore wind energy.